The present invention generally relates to a heater system for an air intake of an automotive vehicle. More particularly, the present invention relates to a stand alone heater control system which incorporates pulse width modulation to produce a desired intake air heating cycle.
Electrically powered air intake heaters are useful for heating air as it enters the intake of an internal combustion engine. Depending on the thermal conditions of the engine and the ambient air, it may be desirable to heat the intake air prior to attempting to start the engine. Typically, the air is heated for a predefined time based on the ambient air temperature.
Many air intake heaters are coupled to an electrical circuit including a battery, a battery cable, a common connector, another wire, a fuse, yet another wire, a relay and a final wire to the air heater. The relay is typically controlled by the engine electronic control module. Based on signals received from the electronic control module, the relay supplies current to the heater or does not. In addition to the plurality of wires noted in the above circuit, metal supports and hardware are required to attach the components to the vehicle.
Additionally, the heater is typically sized to provide a desired wattage based on engine size and duty cycle. Typically, air heaters are sized such that the full battery voltage and current may be supplied to the heater for a defined period of time. This control scheme often requires the heater to be energized for approximately thirty seconds when ambient temperatures are low such as minus twenty degrees Fahrenheit. While heaters controlled and sized in this manner have been effective, improvements may exist.
An air intake heater system of the present invention includes a controller coupled to the air heater. The controller and air heater are designed so that they can preferably be coupled to the battery using a single wire. The controller may function as a stand alone unit or may accept data from the vehicle electronic control module. The controller of the present invention utilizes a pulse width modulation control scheme where the total energy per unit time output from the air heater is controlled. Therefore, a larger air heater may be implemented than previously used. By implementing a larger air heater, the time required to preheat the air is drastically reduced. In addition, production efficiencies can be achieved since the same heater construction can be used for different engines.
Preferably, the air heater system of the present invention collects engine rpm data after the engine has been started. The system utilizes the data to determine the duration and quantity of energy output from the heater after engine starting to ensure smooth idle. In this manner, the total energy output by the air heater is minimized. In addition, the emissions and running characteristics during initial start up are improved.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.